Transistors



Oct; 22,1957 4 R. D. KNOTT 2,810,873

TRANSISTORS Filed Aug. 10, 1956 '0 I 7 lNvEN-roR m? .DFIVID T agumgdl aagw United States Patent TRANSISTORS Ralph David Knott, North Greenford,England, assignor to The General Electric Company Limited, London, 7

This invention relates to transistors.

It is desirable that the heat generated in a transistor during operationshould be efiiciently dissipated, since the characteristics of atransistor deteriorate at elevated temperatures and this factor normallyimposes a limit on the power handling capacity of the transistor.

It is an object of the present invention to provide a tran sistordesigned in accordance with this requirement, without involving unduestructural complexity.

According to the invention, there is provided a transistor comprising asemiconductor body having in contact therewith emitter, collector andbase electrodes, said body being housed in an envelope of which at leastthe major part is metal, and the base electrode being constituted by arelatively massive metallic member to which the semiconductor body isintimately connected over an appreciable area and part of which bearsresiliently over an appreciable area against the internal surface of ametallic part of the envelope.

One arrangement in accordance with the invention will now be describedby way of example with reference to the accompanying drawings, in which:

Figure l is a sectional view of a germanium junction transistor, thesection being along the line II in Figure 2; and

Figure 2 is a section on the line ll-il in Figure 1.

Referring to the drawings, the transistor includes a square plate 1 ofN-type germanium which is provided with emitter and collector electrodes2 and 3 respectively, the electrodes 2 and 3 being centrally disposed onopposite main faces of the plate 1. The electrodes 2 and 3 are formed inknown manner by fusing small quantities of indium to the appropriatefaces of the plate 1 and are respectively provided with leads in theform of line wires 4 and 5 whose ends are respectively embedded in theindium beads thus produced. The main face of the germanium plate 1 onwhich the emitter electrode 2 is disposed is soldered to a baseelectrode 6 formed from sheet metal, the base electrode 6 being in thegeneral form of a channel member of U-shaped cross-section havingpressed into its base a square well 7 extending into the interior of theU. This well 7 serves to locate the germanium plate 1, which is solderedto the base electrode 6 at the bottom of the well 7, a centrallydisposed circular hole 8 having a diameter somewhat less than the lengthof a side of the germanium plate 1 being provided in the base electrode6 to accommodate the emitter electrode 2.

The unit described above is mounted on a support con- Patented 2.2, 1957sisting of a copper skirt 9 in which is sealed a glass bead 10 throughwhich are sealed three wires 11, 12 and 13. The wires 11, 12 and 13 arerespectively welded to the emitter and collector lead wires 4 and 5 anda tag 14 formed on the base electrode 6. The main part of the envelopeof the transistor is constituted by a circular cylindrical copper cap 15into which the mounted unit is inserted with the skirt 9 disposed in theopen end of the cap 15 and with the longitudinal axis of the baseelectrode 6 extending parallel to the axis of the cap 15. The baseelectrode 6 is initially made of such a size that when it is insertedinto the cap 15 the arms of the base electrodes 6 are pushed inwards, sothat they bear resiliently on the internal surface of the cap 15; thecorners of the base electrode 6 at the end which is inserted first aresuitably rounded to facilitate insertion.

The envelope is hermetically sealed by cold pressure welding togetherflanges 16 and 17 respectively formed on the outer ends of the skirt 9and the cap 15, the welding being carried out in an atmosphere of drynitrogen so as to provide a permanent inert gas filling for theenvelope. Finally, the space within the skirt 9 is filled with anelectrically insulating synthetic resin 18.

It will be appreciated that in the arrangement described above the formof the base electrode 6 is such that there is a good thermal connectionbetween the germanium plate 1 and the copper cap 15, this materiallyassisting in the eificient dissipation of heat generated duringoperation of the transistor; it will further be appreciated that thisresult is achieved without requiring any extra joints to be made betweenparts of the transistor over and above the case where no such thermalconnection is provided.

In an alternative arrangement to that described above the base electrodemay be provided with one or more tongues projecting transversely to itslongitudinal axis and arranged to bear resiliently on the closed end ofthe cap when the base electrode is inserted into the cap.

I claim:

1. A transistor comprising a semiconductor body having in contacttherewith emitter, collector and base electrodes, said body being housedin an envelope of which at least the major part is metal, and the baseelectrode being constituted by a relatively massive metallic member towhich the semiconductor body is intimately connected over an appreciablearea and part of which bears resiliently over an appreciable areaagainst the internal surface of a metallic part of the envelope.

2. A transistor according to claim 1, in which the main part of theenvelope is constituted by a metal cap in the open end of which issealed a support on which the base electrode is mounted, the baseelectrode being in the general form of a channel member of U-shapedcross-section of such a size that when the base electrode is insertedinto the cap the arms of the base electrode are pushed inwards so thatthey bear resiliently on the internal surface of the cap.

References Cited in the file of this patent UNITED STATES PATENTS2,615,965 Amico Oct. 28, 1952 2,661,448 Rodgers Dec. 1, 1953 2,673,311Amico Mar. 23, 1954

